Mechanical compressors, such as electrically driven, multi-stage cylinder compressors are well-known in the art. The term compressor here should be understood to refer to a device for delivering compressed gas (including air), for example to a pressure tank or for direct use.
Such compressors require cooling. There is partly a need for cooling of the compressed gas delivered by the compressor, and partly for cooling of the actual compressor in order to avoid overheating and mechanical damage. In the case of multi-stage compressors there is also a need for cooling of the compressed gas between one stage and the next.
Solutions are previously known for air cooling of compressors. For example, it is previously known to place an axial fan in the extension of the compressor's drive shaft or a separately driven fan with, for example, an electromotor in front of the compressor, in order thereby to provide a movement of heated air from the compressor housing and from the gas coolers (i.e. the heat exchangers) that are connected after the individual compressor stage.
According to many known solutions the same air will cool the compressor's heat exchangers and hot surfaces. This results in less efficient cooling of hot surfaces since the cooling air is already heated by the heat exchangers. In other previously known solutions the same air will cool the compressor's hot surfaces before cooling the heat exchangers. In these cases the cooling of the heat exchangers will be less efficient since the cooling air is already heated by the hot surfaces. In most of the known cases the compressor draws in air that is heated by the heat exchangers and/or the hot surfaces. This reduces the efficiency and increases the need for cooling of compressed air and of the components that are in contact with the compressed air. In previously known solutions the cooling air will not be passed as efficiently over the parts that require cooling. A portion of the air will pass outside and is therefore ineffective. A relatively large and energy-demanding fan is required to compensate for this loss.
According to previously known solutions open uncovered compressor structures have been employed to a great extent with the object of increasing the air replacement and thereby increasing cooling efficiency. Such open structures cause the compressor to produce more noise and it is more exposed to external influences such as, for example, dust, particles, water splashes and blows. At the same time hot surfaces and sharp edges on the compressor will represent a safety risk.